The push-broom principle is illustrated in FIG. 1 diagrammatically in the case of a strip of detectors 1. This strip on board the satellite carries out the successive observation, as the satellite moves, of rows L1, L2, . . . , LN perpendicular to the direction of displacement D. A wide field optic 2 forms the image of the ground on a row of detectors located in the focal plane. The row scan is obtained by reading the sensitive elements of the detection row. The scan of the landscape in the perpendicular direction results from the movement of the satellite in its orbit. It is also possible to use a spectral splitter that makes it possible in addition to conduct this observation in different spectral windows and thus produce the multispectral imaging.
In a known manner when wanting to produce a polychromatic image, strips of individual detectors are used that are coupled to interference filters as illustrated in FIG. 2 that represent the example of four filters having respective spectral bands B0, B1, B2, B3 physically separated by a distance Li-j. Notably, it is known to use filters of small thickness called “match” filters. To reconstruct the various spectral components, a detector coupled to four filters of very small thickness can conventionally be used. These filters are difficult to manufacture because they are made up of stacks of thin layers on the surface of a substrate. FIG. 3 shows an example of layer stacking, typically around 20 layers distributed over both faces of a substrate may be necessary to form a filter in a given wavelength range. This type of filter notably has two types of drawbacks. The first is associated with the edge effects in an area zi that appear because of the stacking of all of these layers with a thickness of the order of λ/4 and that, given a large number of layers, embrittle the filters. The second drawback is associated with the fact that the various filters are produced in a connected way on one and the same substrate as illustrated in FIG. 3 that diagrammatically represents the production of two types of stacking that make it possible to provide filtering functions in wavelength bands Bi and Bj. The layer stacking technologies entail imposing minimum separation distances between two filters, of the order of a few millimeters, which amounts to taking images of scenes on the ground that are several kilometers away.